In the production of glass fibers usable in the form of "wool" batts for insulation purposes, one of the more widely used processes is a centrifugal process in which glass, at temperatures above its liquidus, is emitted through the apertures of a rapidly rotating spinner. The glass is further attenuated by contact with blasts of hot gases, such as steam or combustion gases. The attenuated fibers are contacted with a binder, frequently of a phenol-formaldehyde or phenol-urea type, and are collected on a moving conveyor in the form of batts which are subsequently dried and packaged for shipment as insulation.
The composition of the chemicals which are combined to form the "batch", which is subsequently melted to form the glass, is important for many reasons, one of which is cost and a second of which includes the general properties of the batt itself, particularly as evidenced by the dry strength and water durability of the fibers contained therein.
There now has been discovered a glass composition which is less expensive than conventional batches and which, more importantly, in the form of fibers, reacts with phenol-based binders to facilitate the adherence of the pack as a unit and, hence, improves dry strength. These fibers also possess improved water durability.